JP4857822B2 - Droplet discharge head and droplet discharge apparatus - Google Patents

Description

  The present invention relates to a droplet discharge head that discharges droplets and a droplet discharge apparatus that includes the droplet discharge head.

  As a droplet discharge head that discharges droplets, ink jet recording is performed by pressurizing ink supplied from a supply path to a pressure chamber, discharging ink droplets from nozzles communicating with the pressure chamber, and recording an image on a recording medium. The head is known.

In such an ink jet recording head, there has been proposed an ink jet recording head in which a filter for filtering ink is provided on the upstream side of a supply path so as to correspond to each nozzle on a one-to-one basis (Patent Documents 1 and 2). 2).
JP 2003-311952 A JP 2003-311984 A

  As described above, in an ink jet recording head provided with a filtration filter, a vibration system formed between the nozzle and the ink supply path and a vibration system formed between the ink supply path and the filtration filter are provided. , The combined form.

  In the conventional structure of an ink jet recording head without a filter, the structure and driving waveform of the ink jet recording head are determined in consideration of only the vibration system formed between the nozzle and the ink supply path. It was.

  As described above, in an inkjet head having a filtration filter for each nozzle, when the structure is determined by the conventional method, the vibration of the pressure wave formed by the vibration system from the filtration filter to the ink supply path is generated from the nozzle to the ink supply path. It overlaps with the vibration of the pressure wave formed in the vibration system up to.

  For this reason, in order to suppress the reverberation of a pressure, the drive waveform of the drive signal to apply becomes a complicated thing, and becomes a subject.

  In consideration of the above fact, the present invention can suppress the reverberation of a pressure wave without using a complicated driving waveform as a driving signal to be applied in a droplet discharge head having a filtration filter corresponding to each nozzle. The purpose is to do.

  A droplet discharge head according to a first aspect of the present invention includes a nozzle that communicates with a plurality of pressure chambers, discharges liquid in a pressure chamber to which pressure is applied, and a passage provided on the upstream side of the pressure chamber. And the pressure chamber, and a liquid supply head for supplying the liquid sent from the passage to the pressure chamber, and a filtration filter provided in the passage for filtering the liquid. The resonance frequency of the first vibration system formed between the nozzle and the supply path is fc, and the resonance frequency of the second vibration system formed between the filtration filter and the supply path is fo. In this case, (n−0.3) × fc ≦ fo ≦ (n + 0.3) × fc (n is a positive integer).

  According to this configuration, the filter provided in each passage filters the liquid, and the liquid is sent from the passage to the supply path. The liquid sent to the supply path is supplied to the pressure chamber. The liquid in the pressure chamber is discharged from the nozzle under pressure.

  Here, in the first aspect of the present invention, the resonance frequency of the first vibration system formed between the nozzle and the supply path is fc, and the second vibration system formed between the filtration filter and the supply path. When the resonance frequency is fo, a relationship of (n−0.3) × fc ≦ fo ≦ (n + 0.3) × fc (n is a positive integer) is established.

  Thus, in the configuration of the first aspect, since the resonance frequency fo of the second vibration system is equal to an integral multiple of the resonance frequency fc of the first vibration system or an approximate value of an integer multiple, the second vibration system The timing of the drive signal to be applied to cancel the reverberation generated by the first vibration system and the reverberation generated by the second vibration system after the vibration of the first vibration system and the node of the vibration of the first vibration system are substantially coincident and the liquid is ejected. Can be substantially matched.

  Since the timing for canceling the reverberation can be made substantially the same, the reverberation of the pressure wave can be suppressed without complicating the drive waveform of the drive signal applied to the piezoelectric actuator that applies pressure to the liquid in the pressure chamber.

  The resonance frequency fo of the second vibration system is not limited to the case where the resonance frequency fo of the second vibration system completely coincides with an integer multiple of the resonance frequency fc of the first vibration system, and the resonance frequency fo of the second vibration system is the resonance frequency fc of the first vibration system. In the range of (n−0.3) times to (n + 0.3) times, the reverberation of the pressure wave can be suppressed without using a complicated drive waveform for the applied drive signal. On the other hand, when the resonance frequency fo of the second vibration system is outside the range of (n−0.3) to (n + 0.3) times the resonance frequency fc of the first vibration system, the reverberation of the pressure wave In order to suppress this, it is necessary to largely shift the timing for canceling the reverberation, and the drive waveform of the drive signal to be applied becomes complicated.

  According to a second aspect of the present invention, there is provided a liquid droplet ejection apparatus comprising the liquid droplet ejection head according to the first aspect.

  Since the present invention has the above-described configuration, the reverberation of the pressure wave can be suppressed without using a complicated drive waveform for the drive signal to be applied.

  Hereinafter, an example of an embodiment according to a droplet discharge head of the present invention and a droplet discharge apparatus including the droplet discharge head will be described with reference to the drawings.

  In the present embodiment, a droplet discharge head that discharges droplets and a droplet discharge device that includes the droplet discharge head include an inkjet recording head that discharges ink and records an image on a recording medium, and the inkjet recording head. An ink jet recording apparatus will be described.

  First, the outline of the ink jet recording apparatus 10 will be described with reference to FIG. The recording medium will be described as recording paper P. In FIG. 1, the conveyance direction of the recording paper P in the inkjet recording apparatus 10 is represented by an arrow S as a sub-scanning direction, and the direction orthogonal to the conveyance direction is represented by an arrow M as a main scanning direction.

  As shown in FIG. 1, an ink jet recording apparatus 10 according to this embodiment includes a carriage 12 on which black, yellow, magenta, and cyan ink jet recording heads 30 are mounted. The carriage 12 has a pair of brackets 14 projecting upstream in the conveyance direction of the recording paper P (only one bracket 14 is shown in the figure), and circular holes 14A formed in the pair of brackets 14 respectively. The shaft 20 is inserted in the main scanning direction.

  A driving pulley (not shown) and a driven pulley (not shown) constituting the main scanning mechanism are disposed on both ends in the main scanning direction with respect to the carriage 12. A part of the timing belt 22 that is wound around the drive pulley and the driven pulley and travels in the main scanning direction is fixed to the carriage 12. As a result, when the timing belt 22 travels in the main scanning direction by the rotational driving of the driving pulley, the carriage 12 reciprocates in the main scanning direction with the pair of brackets 14 being guided by the shaft 20.

  A paper feed tray 26 for storing recording paper P before image recording in a bundle is provided at the lower front side of the inkjet recording apparatus 10. Disposed above the paper feed tray 26 is a paper discharge tray 28 from which the recording paper P on which images are recorded by the ink jet recording heads 30 of the respective colors is discharged. Also, below the carriage 12 and the shaft 20, there is a sub-scanning mechanism 18 including a transport roller and a discharge roller that transport the recording paper P fed one by one from the paper feed tray 26 in the sub-scanning direction at a predetermined pitch. Is provided.

  In addition, the inkjet recording apparatus 10 is provided with a control panel 24 for performing various settings during image recording, a maintenance station (not shown), and the like. The maintenance station includes a cap member, a suction pump, a dummy jet receiver, a cleaning mechanism, and the like, and performs maintenance operations such as a suction recovery operation, a dummy jet operation, and a cleaning operation.

  Also, a plurality of nozzles 46 (see FIG. 2) for ejecting ink droplets are formed on the lower surface (ink ejection surface) of the ink jet recording head 30 for each color so as to face the recording paper P.

  The ink jet recording apparatus 10 according to this embodiment is a so-called Partial Width Array (PWA) type ink jet recording apparatus configured as described above, and operates as follows.

  That is, in the ink jet recording apparatus 10 according to the present embodiment, ink droplets are selectively ejected from the nozzles 46 of the ink jet recording head 30 onto the recording paper P while the ink jet recording head 30 is moved in the main scanning direction by the main scanning mechanism. As a result, a part of the image based on the image data is recorded in a predetermined band area.

  When one movement in the main scanning direction is completed, the recording paper P is conveyed by a predetermined pitch in the sub scanning direction by the sub scanning mechanism 18, and the ink jet recording head 30 is again moved in the main scanning direction (the direction opposite to the above). A part of the image based on the image data is recorded in the next band area while moving to the next band area. By repeating such an operation a plurality of times, the entire image based on the image data is recorded on the recording paper P. The image is recorded in full color.

  Next, the ink jet recording head 30 mounted on the ink jet recording apparatus 10 according to the present embodiment will be described.

  As shown in FIGS. 2 and 3B, the ink jet recording head 30 according to the present embodiment includes a nozzle plate 32, a first communication path plate 34, a pressure chamber plate 36, a vibration plate 38, a supply path plate 40, a first plate. A dual communication path plate 42 and a filtration filter plate 44 are provided.

  The nozzle plate 32, the first communication path plate 34, the pressure chamber plate 36, the vibration plate 38, the supply path plate 40, the second communication path plate 42, and the filtration filter plate 44 are stacked in this order, and the plates are joined to each other. Yes.

  As shown in FIGS. 2, 3A and 3B, the nozzle plate 32 is formed with a plurality of nozzles 46 each having a circular through hole. These nozzles 46 are arranged in a matrix at predetermined intervals. Has been placed.

  In the first communication path plate 34, first communication paths 48 each formed of a circular through hole having a diameter slightly larger than the nozzle diameter are formed in the upper positions corresponding to the nozzles 46 of the nozzle plate 32. The first communication path 48 communicates with the nozzle 46 so that ink can flow from the first communication path 48 to the nozzle 46.

  In the pressure chamber plate 36, cavities 51 that are open in the vertical direction are formed at positions above the first communication passages 48 of the first communication passage plate 34.

  The pressure chamber plate 36 is sandwiched and joined between the first communication path plate 34 and the vibration plate 38, and the lower open portion of the cavity 51 is covered with the first communication path plate 34 and the cavity 51 is opened. The upper part is covered with the diaphragm 38. As a result, a pressure chamber 50 having a predetermined size is formed. One end of the pressure chamber 50 communicates with the first communication path 48, and ink can flow from the pressure chamber 50 to the first communication path 48.

  The diaphragm 38 is formed with a fitting hole 58 made of a circular through hole at a position above the other end of the pressure chamber 50 of the pressure chamber plate 36.

  In the supply path plate 40, supply paths 52 each including a circular through hole having a diameter slightly smaller than the diameter of the fitting hole 58 are formed at an upper position corresponding to the fitting hole 58 of the diaphragm 38. A protruding portion 60 that protrudes toward the diaphragm 38 (downward) is formed on the outer peripheral portion of the supply path 52, and the protruding portion 60 is configured to fit into the fitting hole 58. The supply path 52 communicates with the other end of the pressure chamber 50 and can supply ink from the supply path 52 to the pressure chamber 50.

  In addition, a space portion 62 having a predetermined size is formed in the supply path plate 40 above the pressure chamber 50. A piezoelectric actuator 64 made of a piezoelectric element is disposed in the space portion 62, and the piezoelectric actuator 64 is attached to the upper surface of the vibration plate 38 located above the pressure chamber 50.

  The piezoelectric actuator 64 is deformed so as to reduce the volume in the pressure chamber 50 by applying an electric signal (drive signal), and applies pressure to the pressure chamber 50. Accordingly, ink is sent from the pressure chamber 50 to the first communication path 48.

  The supply path plate 40 is formed with first electrical connection holes 66 each having a circular through hole. The first electrical connection hole 66 is placed on the upper surface of the end portion 64A of the piezoelectric actuator 64 formed in a circular shape.

  In the second communication path plate 42, second communication paths 54 each having a circular through-hole having a diameter larger than the diameter of the supply path 52 are formed at upper positions corresponding to the supply paths 52 of the supply path plate 40. Yes. That is, the second communication passage 54 has a larger passage area than the supply passage 52. The second communication path 54 communicates with the supply path 52 and can circulate ink to the supply path 52.

  The inner wall surface of the second communication path 54 is inclined from the filtration filter plate 44 toward the supply path plate 40, and the second communication path 54 extends from the filtration filter plate 44 (upper side) to the supply path plate 40 (lower side). It is formed in a taper shape that is gradually reduced in diameter. The wall surface of the second communication path 54 is formed of glass, metal, Si, or the like. The second communication passage 54 corresponds to the passage provided on the upstream side of the pressure chamber.

  The second communication path plate 42 includes a second through hole having a circular through hole having a diameter larger than the diameter of the first electrical connection hole 66 at an upper position corresponding to each first electrical connection hole 66 of the supply path plate 40. Electrical connection holes 68 are respectively formed. The second electrical connection hole 68 has the same shape as the second communication passage 54.

  A wiring pattern 70 is formed on the upper surface of the second communication path plate 42 (see FIG. 2). One end portion of the wiring pattern 70 extends to the inner wall surface of the first electrical connection hole 66 and the second electrical connection hole 68 and is electrically connected to the circular end portion 64 </ b> A of the piezoelectric actuator 64.

  The other end of the wiring pattern 70 is electrically connected to a drive IC (not shown). The drive IC receives a control signal from the outside, determines a drive waveform based on the control signal, transmits an electric signal (drive signal) to the piezoelectric actuator 64, and drives each piezoelectric actuator 64 at a predetermined timing. Let

  The filtration filter plate 44 is provided with a filtration filter 56 for filtering ink at an upper position corresponding to the second communication path 54 of the second communication path plate 42, and the filtration filter 56 is located above the supply path 52. It is provided at a position (in detail, vertically above).

  A plurality of filter holes 56A are formed in the filtration filter 56, and the ink passes through the filter holes 56A, so that impurities in the ink are removed. Discharged. The filtration filter 56 is provided at a position above the second communication path 54, but may be configured to be provided in the flow path of the second communication path 54.

  A single common supply path (not shown) for supplying ink from an ink pool (not shown) to each second communication path 54 is provided above the filter plate 44. In addition, there may be a configuration in which there is no common supply path and the ink pool communicates directly with each second communication path 54.

  As described above, the plates 32, 34, 36, 38, 40, 42, 44 are stacked, and the first communication passage 48, the pressure chamber 50, the supply passage 52, and the second communication passage 54 are communicated with each other. A flow path is formed which communicates with the nozzle 46 and sends ink from the ink tank to the nozzle 46. The first communication path 48, the pressure chamber 50, the supply path 52, and the second communication path 54 that form this flow path may have a cross section other than a circular shape.

Here, the resonance frequency fc of the first vibration system formed between the supply path 52 and the nozzle 46 and the resonance frequency fo of the second vibration system formed between the supply path 52 and the filtration filter 56 are: It is calculated by the following equation, and in this embodiment, (n−0.3) × fc ≦ fo ≦ (n + 0.3) × fc (n is a positive integer).
fc = 2π (m2 × m3 / (m2 + m3) × c1) ^ (1/2) (1)
fo = 2π (m2 × m0 / (m2 + m0) × c0) ^ (1/2) (2)
m2: supply path inertance, m3: nozzle inertance, m0: filtration filter inertance, c1: pressure chamber acoustic capacity, c0: second communication path acoustic capacity.

  The vibration A of the pressure wave generated by the first vibration system and the vibration B of the pressure wave generated by the second vibration system when the resonance frequency fo of the second vibration system is equal to an integral multiple of the resonance frequency fc of the first vibration system are shown in FIG. The vibration history shown in FIG. 4 is such that the vibration of the second vibration system and the node of the vibration of the first vibration system coincide with each other.

  Generated by the vibration A of the pressure wave generated by the first vibration system and the second vibration system when the resonance frequency fo of the second vibration system is equal to an approximate value (± 30%) of an integral multiple of the resonance frequency fc of the first vibration system. The vibration B of the pressure wave becomes the vibration history shown in FIG. 5, and the portion of the vibration of the second vibration system and the portion of the vibration of the first vibration system are substantially matched.

  As shown in FIGS. 3A and 3B, the thickness of each plate is, for example, 0.025 mm for the nozzle plate 32, 0.2 mm for the first communication path plate 34, and the pressure chamber plate 36. Is 0.1 mm, the supply path plate 40 is 0.04 mm, the second communication path plate 42 is 0.3 mm, and the filtration filter plate 44 is 0.02.

  The nozzle diameter of the nozzle 46 is, for example, 0.025 mm, and the diameter of the first communication path 48 is, for example, 0.09 mm. The width of the pressure chamber 50 is, for example, 0.6 mm, and the depth of the pressure chamber 50 is, for example, 0.18 mm.

  The diameter of the supply path 52 is, for example, 0.03 mm, the minimum diameter of the second communication path 54 is, for example, 0.1 mm, and the maximum diameter of the second communication path 54 is, for example, 0.22 mm. ing. The diameter of the filtration filter 56 is, for example, 0.22 mm, and the diameter of the filter hole 56A of the filtration filter 56 is, for example, 0.015 mm.

  According to this configuration, the resonance frequency fo of the second vibration system is an approximate value (fo / fc≈6.84) that is an integral multiple of the resonance frequency fc of the first vibration system.

  Next, the operation of the above embodiment will be described.

  In image recording by the ink jet recording head 30 according to the present embodiment, first, ink stored in the ink pool passes through the filtration filter 56, is filtered, and is sent to the second communication path 54.

  The ink sent to the second communication path 54 is supplied to the pressure chamber 50 through the supply path 52 and further filled from the pressure chamber 50 to the nozzle 46 through the first communication path 48.

  When an electric signal (driving signal) is applied to the piezoelectric actuator 64 in a state where the ink is filled, the piezoelectric actuator 64 is deformed so as to decrease the volume in the pressure chamber 50 and applies pressure to the pressure chamber 50. . As a result, the ink in the pressure chamber 50 is pressurized and discharged as ink droplets from the nozzle 46 via the first communication path 48.

  Here, in the present embodiment, for example, the resonance frequency fo of the second vibration system is equal to an integral multiple of the resonance frequency fc of the first vibration system, so that the vibration by the second vibration system and the first vibration system The timing of canceling the reverberation generated by the first vibration system and the reverberation generated by the second vibration system after the portions of the vibration nodes coincide and the ink droplets are ejected can be matched.

  For example, as shown in FIG. 4, a negative-pressure drive waveform having an opposite phase is applied to the piezoelectric actuator 64 in a state where the vibration by the second vibration system and the vibration by the first vibration system are both positive. Thus, reverberation can be suppressed and ink droplet ejection efficiency can be increased (refer to the arrows in FIG. 4 for the timing of applying the drive signal).

  In this way, the timing for canceling the reverberation can be matched, so that the drive waveform of the drive signal applied to the piezoelectric actuator 64 is not complicated.

  The resonance frequency fo of the second vibration system is not limited to an integer multiple of the resonance frequency fc of the first vibration system, and the resonance frequency fo of the second vibration system is (n−0.3) times to ( If it is in the range of (n + 0.3) times, the above effect can be obtained.

  When exceeding this range, in order to suppress the reverberation due to the first vibration system and the reverberation due to the second vibration system, it is necessary to largely shift the timing for canceling the reverberation. The drive waveform of the drive signal to be applied becomes complicated.

  The ink jet recording apparatus according to the present embodiment is a so-called “Partial Width Array (PWA)” type. However, as the liquid droplet ejection apparatus according to the present invention, an effective recording area has a width of the recording paper (conveying direction and 4 ink jet recording heads corresponding to four colors of yellow (Y), magenta (M), cyan (S), and black (K) respectively. A so-called full width array (FWA) type that records a full-color image may be used.

  In this embodiment, an ink jet recording apparatus that discharges ink droplets and records an image is described as a liquid droplet discharging apparatus that discharges liquid droplets, and ink is discharged as a liquid droplet discharging head that discharges liquid droplets. The ink jet recording head for recording an image has been described. However, the droplet discharge device and the droplet discharge head according to the present invention are not limited to those that record an image on a recording sheet, and the liquid to be discharged is not limited to ink.

  For example, it is used industrially, such as a device that creates a color filter for display by discharging ink onto a polymer film or glass, or a device that forms bumps for component mounting by discharging solder in a welded state onto a substrate. The present invention can be applied to a droplet discharge device and a droplet discharge head in general used in the droplet discharge device.

  The present invention is not limited to the above-described embodiment, and various modifications, changes, and improvements can be made without departing from the gist of the present invention.

FIG. 1 is a diagram showing an overall configuration of an ink jet recording apparatus according to an embodiment of the present invention. FIG. 2 is a perspective view showing the internal configuration of the ink jet recording head according to the present embodiment with a partial cutaway. FIG. 3A is a plan view showing the ink jet recording head according to this embodiment, and FIG. 3B is a cross-sectional view taken along line 3B-3B of FIG. FIG. 4 shows pressure waves generated by the first vibration system and pressure wave vibrations generated by the second vibration system when the resonance frequency of the second vibration system according to the present embodiment is equal to an integral multiple of the resonance frequency of the first vibration system. It is a figure which shows a log | history. FIG. 5 shows pressure waves generated by the first vibration system when the resonance frequency of the second vibration system according to the present embodiment is equal to an approximate value (± 30%) that is an integral multiple of the resonance frequency of the first vibration system. It is a figure which shows the vibration history of the pressure wave produced by a 2 vibration system.

Explanation of symbols

10 Inkjet recording device (droplet ejection device)
30 Inkjet recording head (droplet ejection head)
46 Nozzle 48 Communication passage (passage)
52 Supply path 56 Filtration filter

Claims (2)

A nozzle that communicates with each of the plurality of pressure chambers and discharges liquid in the pressure chamber to which pressure is applied;
A supply path that connects the passage provided on the upstream side of the pressure chamber and the pressure chamber, respectively, and supplies the liquid sent from the passage to the pressure chamber;
A filtration filter provided in each of the passages for filtering the liquid;
A liquid droplet ejection head comprising:
When the resonance frequency of the first vibration system formed between the nozzle and the supply path is fc and the resonance frequency of the second vibration system formed between the filtration filter and the supply path is fo, n−0.3) × fc ≦ fo ≦ (n + 0.3) × fc (n is a positive integer).   A droplet discharge apparatus comprising the droplet discharge head according to claim 1.

Images